This invention relates to a prober and a probe method, and more particularly a prober capable of bringing a plurality of probes formed on a probe card into contact with the electrodes of a substrate with a constant and optimum pressure.
FIGS. 11, 12 show a prober for testing the electrical characteristic of a semiconductor integrate circuit (which is hereinafter referred to as an "IC chip") formed on a semiconductor wafer (which is hereinafter referred to as a "wafer") as an example of a conventional prober. The conventional prober includes a loader chamber 1 in which the wafer W is pre-aligned and a prober chamber 2 for testing the electrical characteristic of the wafer W carried therein from the loader chamber 1. As shown in FIG. 12, a fork 3 and a sub-chuck 4 are disposed in the loader chamber 1. The wafer W is pre-aligned by the sub-chuck 4 with the orientation flat thereof used as a reference while it is being carried by the fork 3. A main chuck 5 and an alignment mechanism 6 having upper and lower cameras are disposed in the prober chamber 2. The main chuck 5 having the wafer W mounted thereon can be moved in X, Y, Z and .theta. directions and is controlled by the alignment mechanism 6 so as to align the wafer W with probes (for example, probe needles) 7A of a probe card 7. After the alignment, the main chuck 5 rises, the probes 7A are set into electrical contact with the electrodes of the IC chip (S) formed on the wafer W mounted on the main chuck 5 and the electrical characteristic of the wafer W is tested via a test head T connected to the probes 7A. A temperature adjustment mechanism is disposed on the main chuck 5. The temperature of the wafer W can be set in a wide range of -50.degree. C. to +160.degree. C., for example, by the temperature adjustment mechanism. The wafer W can be subjected to the normal temperature test, low-temperature test, and high-temperature test.
At the time of test, the temperature of the main chuck 5 is set to a preset test temperature by the temperature adjustment mechanism. The wafer W mounted on the main chuck 5 is controlled by moving the main chuck 5 in the X, Y directions by use of the alignment mechanism 6 so as to align the probes 7A with the electrodes of the IC chip formed on the wafer W. The main chuck 5 thus aligned is raised to set the probes 7A into electrical contact with the electrodes of the IC chip (S) formed on the wafer W. A test portion and the electrodes of the IC chip (S) are connected together via the probes 7A and test head T and then the electrical characteristic of the IC chip (S) is tested. The probe card 7 is removably mounted on a head plate 8 which forms the top panel of the prober chamber 2.
As shown in FIG. 11, the main chuck 5 is mounted on X and Y tables 9 (the X table and Y table are shown as integrally formed in the drawing for convenience of the explanation) which are separately and reciprocally moved in the X direction and Y direction and is reciprocally moved in the X and Y directions according to the movement of the X and Y tables 9. As schematically shown in FIG. 13, an elevating mechanism 10 for moving the main chuck 5 in the Z direction is disposed on the X, Y tables 9. For example, the elevating mechanism 10 includes a motor 10B set in a hollow cylindrical container 10A, a ball screw 10C rotated by the motor 10B, and a nut member (not shown) engaged with the ball screw and the main chuck 5 is moved up and down by means of the nut member according to the rotation of the ball screw 10C in the direction indicated by the arrow Z in the drawing. As is well known in the art (FIG. 11), the traveling distance of the main chuck 5 in the vertical direction at the time of test is measured by use of the upper camera 6A, lower camera 6B and target 6C of the alignment mechanism 6, for example. The elevating mechanism 10 is driven according to the measurement data. The probes 7A, target 6C and wafer W are photographed by use of the upper camera 6A and lower camera 6B and the above traveling distance in the vertical direction is calculated based on position coordinate data of the main chuck 5 in the respective photographing positions.
In the days in which the wafer size ranges from 6 in. or 8 in. to 12 in., the wafer size is not only increased but also the integrated circuit is miniaturized and the pitch between electrode pads becomes increasingly smaller. For this reason, the conventional prober has problems to be solved. For example, when the IC chip S lying on the peripheral portion of the wafer W are tested, for example, a unbalanced load which is as large as several kilograms is applied to the main chuck 5. This phenomenon becomes more significant as the number of terminals such as the probes 7A increases when a plurality of chips are simultaneously tested, for example. As exaggeratingly indicated by the one-dot-dash line in FIG. 13, the X and Y tables 9 are bent by inclination of the main chuck 5 and the contact pressure (needle pressure) between a plurality of probes 7A and the electrodes of the IC chip (S) on the wafer W fluctuates. Therefore, the reliability of test may be lowered. If the wafer size becomes as large as 12 in., the distance from the center of the main chuck to an acting point becomes longer than the conventional case. Inclination of the main chuck 5 becomes significant and the fluctuation in the pressure of the contact with the plurality of probes 7A becomes significant. In some cases, some of the probes 7A may not be brought into contact with the electrodes of the IC chip (S) on the wafer W. There is a possibility that the reliability will be extremely lowered.
In the conventional prober, the distance between the wafer W on the main chuck 5 and the probes 7A is derived by use of the depths of focus of the cameras 6A, 6B of the alignment mechanism 6. The distance measurement by focusing of the cameras 6A, 6B has a limitation. Normally, there occurs a measurement error of 10 .mu.m or more. In the case of a wafer of 12 in., the integration density of the IC chip is extremely enhanced and the film thickness of insulating layers and wiring layers is made increasingly smaller. For example, a membrane contactor or a contactor such as a conventional tungsten needle cannot compensate for the fluctuation in the height direction and the precision (the range of use) in the height direction is limited. In the above contactor, if a measurement error of 10 .mu.m or more occurs in the distance measurement between the wafer W and the probes 7A, the contact pressure of the probes is largely influenced. Thus, it becomes difficult to control the needle pressure to an optimum value. In combination of the inclination of the main chuck 5, a partially excessively high pressure is applied to the probes in an extreme case, and the probes and the IC chip (S) may be damaged.